1. Field of the Invention
The present invention relates to an imaging device such as a color television camera, and more particularly to a device having a structure in which a color-separation prism is combined with solid-state image sensors for respectively receiving component images obtained by said color-separation prism.
2. Related Background Art
The relative positional relationship between a light emitting face in each color channel of the color-separation prism and a light receiving face of the solid state image sensor has to be determined in consideration of the focus light axial adjustment in each color channel, the inclination adjustment of the light receiving face for avoiding image blur at a side of the image field, and the registration adjustment (parallel and rotational displacements in a plane perpendicular to the optical axis) among different color channels. If such adjustments are rendered possible by mounting each solid-state image sensor through an adjustable support mechanism on a substrate or a housing member supporting the color-separation prism, the imaging device itself is inevitably associated with complex support mechanisms. Also there is known, as disclosed in Japanese utility model laid-open No. 111419/1979, a method of adhering each solid-state image sensor directly on the light emitting face of each color channel of the color-separation prism by means of a transparent adhesive material, Though this method enables translational and rotational adjustments in a plane perpendicular to the optical axis, the axial adjustments for focusing and avoiding image blur at one side are not possible.
For enabling the adjustments in the axial direction, Japanese patent laid-open No. 63279/1983 discloses a method of placing a flexible spacer between the rim portions of the light emitting face of the color-separation prism and the light receiving face of the solid-state image sensor and maintaining said spacer in a flexibly deformed state by hardening an adhesive material applied on lateral portions of said spacer. However, if the adhesive material has a large thermal expansion coefficient, the defocusing caused by a temperature change becomes large and not negligible for solid-state image sensors of a high resolving power. Also in this method, the presence of thick adhesive material may cause an error in focus or registration after a prolonged time. It is also proposed to mount the solid-state image sensor with a metal mounting member adhered on the color-separation prism. However, a rapid temperature change may cause damage in the color-separation prism if the thermal expansion coefficient thereof is significantly different from that of the metal mounting member. Also it is hard to remove the dust if deposited in the corner portion of the mutually adhered prism surface and mounting member.
On the other hand, in case of a malfunction in one of the solid-state image sensors, such a defective image sensor has to be peeled off from the color-separation prism for replacement, and such a peeling operation often causes damage on the surface of the prism.
The Japanese utility model laid-open No. 39580/1984 proposes to provide supporting pillars on the light emitting face of the color-separation prism and to connect said pillars with a mounting member for the solid-state image sensor by means of soldering in the same manner as in the connection of electric parts. Although such connection by soldering is convenient for detaching the solid-state image sensor, no disclosure is made as to the fixing method for the pillars.
The Japanese patent laid-open No. 135279/1986 proposes to adhere a support member with an aperture onto the light emitting face of the color-separation prism and to connect, by soldering, plural legs of said support member with the legs of a mounting member supporting the solid-state image sensor. However fine dust particles, eventually deposited in a portion where the rim of the aperture of the support member is in contact with the prism face during the assembling operation, are difficult to remove, and the image quality may deteriorate by the light scattered by remaining dust particles. Furthermore the adhesion of a metal member may result in the drawbacks mentioned above.